1. Field of the Invention
The invention relates to a power supply system and in particular a method for powering a vehicle.
2. Background Art
A variety of vehicles use electricity, and in particular, an electric machine, such as an electric motor, to assist in powering the vehicle. For example, certain electric vehicles are powered exclusively by an electric motor; gasoline or fuel cell hybrid electric vehicles may be selectively powered by an internal combustion engine or an electric motor.
In such vehicles, a high voltage electrical power source, e.g., a high voltage battery, is used to power the high voltage loads of the electric motor. The high voltage electrical power source, in conjunction with a power converter, is also used to support low voltage loads, e.g., a radio, but only after the vehicle is running.
In conventional vehicles, and even in electric or hybrid electric vehicles, a low voltage electrical power source, e.g., a 12 volt battery, is used to power the low voltage loads of the ignition system. Before the ignition system is activated, i.e., when the vehicle is in a key-off state, the low voltage electrical power source also supports other low voltage loads, e.g., an anti-theft device and memory in such devices as radios, clocks, and other electronic devices. These are so-called “key-off” low voltage loads.
Even though the low voltage electrical power source is used to power the low voltage loads of the ignition system and other “key-off” low voltage loads, it occupies space and adds weight to the vehicle. Therefore, a power supply system and method for powering a vehicle that reduce or eliminate the need for a low voltage electrical power source are desired.